Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Article
  • Published:

Generating electricity by moving a droplet of ionic liquid along graphene



Since the early nineteenth century, it has been known that an electric potential can be generated by driving an ionic liquid through fine channels or holes under a pressure gradient. More recently, it has been reported that carbon nanotubes can generate a voltage when immersed in flowing liquids, but the exact origin of these observations is unclear, and generating electricity without a pressure gradient remains a challenge. Here, we show that a voltage of a few millivolts can be produced by moving a droplet of sea water or ionic solution over a strip of monolayer graphene under ambient conditions. Through experiments and density functional theory calculations, we find that a pseudocapacitor is formed at the droplet/graphene interface, which is driven forward by the moving droplet, charging and discharging at the front and rear of the droplet. This gives rise to an electric potential that is proportional to the velocity and number of droplets. The potential is also found to be dependent on the concentration and ionic species of the droplet, and decreases sharply with an increasing number of graphene layers. We illustrate the potential of this electrokinetic phenomenon by using it to create a handwriting sensor and an energy-harvesting device.

This is a preview of subscription content, access via your institution

Access options

Buy this article

Prices may be subject to local taxes which are calculated during checkout

Figure 1: Illustration of the experimental set-up.
Figure 2: Voltage induced in graphene by drawing one or more droplets of 0.6 M NaCl solution.
Figure 3: Mechanism for the drawing potential.
Figure 4: Contact angles and drawing potential for various ionic solutions on monolayer graphene.
Figure 5: Applications of the drawing potential.

Similar content being viewed by others


  1. Delgadoa, A. V. et al. Measurement and interpretation of electrokinetic phenomena. J. Colloid Interface Sci. 309, 194–224 (2007).

    Article  Google Scholar 

  2. Ghosh, S., Sood, A. K. & Kumar, N. Carbon nanotube flow sensors. Science 299, 1042–1044 (2003).

    Article  CAS  Google Scholar 

  3. Zhao Y. et al. Individual water-filled single-walled carbon nanotubes as hydroelectric power converters. Adv. Mater. 20, 1772–1776 (2008).

    Article  CAS  Google Scholar 

  4. Liu, J., Dai, L. & Baur, J. W. Multiwalled carbon nanotubes for flow-induced voltage generation. J. Appl. Phys. 101, 064312 (2007).

    Article  Google Scholar 

  5. Král, P. & Shapiro, M. Nanotube electron drag in flowing liquids. Phys. Rev. Lett. 86, 131–134 (2001).

    Article  Google Scholar 

  6. Yuan, Q. & Zhao, Y. P. Hydroelectric voltage generation based on water-filled single-walled carbon nanotubes. J. Am. Chem. Soc. 131, 6374–6376 (2009).

    Article  CAS  Google Scholar 

  7. Persson, B. N., Tartaglino, J. U., Tosatti, E. & Ueba, H. Electronic friction and liquid-flow-induced voltage in nanotubes. Phys. Rev. B 69, 235410 (2004).

    Article  Google Scholar 

  8. Cohen, A. E. Carbon nanotubes provide a charge. Science 300, 1235–1236 (2003).

    Article  CAS  Google Scholar 

  9. Schedin, F. et al. Detection of individual gas molecules adsorbed on graphene. Nature Mater. 6, 652–655 (2007).

    Article  CAS  Google Scholar 

  10. Robinson, J. T., Perkins, F. K., Snow, E. S., Wei, Z. & Sheehan, P. E. Reduced graphene oxide molecular sensors. Nano Lett. 8, 3137–3140 (2008).

    Article  CAS  Google Scholar 

  11. Wehling, T. O. et al. Molecular doping of graphene. Nano Lett. 8, 173–177 (2008).

    Article  CAS  Google Scholar 

  12. Fowler, J. D. et al. Practical chemical sensors from chemically derived graphene. ACS Nano 3, 301–306 (2009).

    Article  CAS  Google Scholar 

  13. Yin, J., Zhang, Z. H., Li, X. M., Zhou, J. X. & Guo, W. L. Harvesting energy from water flow over graphene? Nano Lett. 12, 1736–1741 (2012).

    Article  CAS  Google Scholar 

  14. Dhiman, P. et al. Harvesting energy from water flow over graphene. Nano Lett. 11, 3123–3127 (2011).

    Article  CAS  Google Scholar 

  15. Newaz, A. K. M., Markov, D. A., Prasai, D. & Bolotin, K. I. Graphene transistor as a probe for streaming potential. Nano Lett. 12, 2931–2935 (2012).

    Article  CAS  Google Scholar 

  16. Nandi, D., Finck, A. D. K., Eisenstein, J. P., Pfeiffer, L. N. & West, K. W. Exciton condensation and perfect Coulomb drag. Nature 488, 481–484 (2012).

    Article  CAS  Google Scholar 

  17. Gorbachev, R. V. et al. Strong Coulomb drag and broken symmetry in double-layer graphene. Nature Phys. 8, 896–901 (2012).

    Article  CAS  Google Scholar 

  18. Weber, C. P. et al. Observation of spin Coulomb drag in a two-dimensional electron gas. Nature 437, 1330–1333 (2005).

    Article  CAS  Google Scholar 

  19. Price, A. S., Savchenko, A. K., Narozhny, B. N., Allison, G. & Ritchie, D. A. Giant fluctuations of coulomb drag in a bilayer system. Science 316, 99–102 (2007).

    Article  CAS  Google Scholar 

  20. Yan, Z. et al. Toward the synthesis of wafer-scale single-crystal graphene on copper foils. ACS Nano 6, 9110–9118 (2012).

    Article  CAS  Google Scholar 

  21. Li, X. et al. Large-area synthesis of high-quality and uniform graphene films on copper foils. Science 324, 1312–1314 (2009).

    Article  CAS  Google Scholar 

  22. Li, X. et al. Transfer of large-area graphene films for high-performance transparent conductive electrodes. Nano Lett. 9, 4359–4363 (2009).

    Article  CAS  Google Scholar 

  23. Lyklema, J. J., de Keizer, A., Bijsterbosch, B. H., Fleer, G. J. & Cohen Stuart, M. A. Fundamentals of Interface and Colloid Science (Academic, 1995).

    Google Scholar 

  24. Kresse, G. & Furthmuller, J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys. Rev. B 54, 11169–11186 (1996).

    Article  CAS  Google Scholar 

  25. Kresse, G. & Furthmuller, J. Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set. Comput. Mater. Sci. 6, 15–50 (1996).

    Article  CAS  Google Scholar 

  26. Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 77, 3865–3868 (1996).

    Article  CAS  Google Scholar 

  27. Kresse, G. & Joubert, D. From ultrasoft pseudopotentials to the projector augmented-wave method. Phys. Rev. B 59, 1758–1775 (1999).

    Article  CAS  Google Scholar 

  28. Kielland, J. Chemical hydration numbers. J. Chem. Educ. 14, 412–413 (1937).

    Article  CAS  Google Scholar 

  29. Makov, G. & Payne, M. C. Periodic boundary conditions in ab initio calculations. Phys. Rev. B 51, 4014–4022 (1995).

    Article  CAS  Google Scholar 

Download references


This work was supported by the 973 program (2013CB932604, 2012CB933403), the National NSF (91023026, 11172124, 51375240, 51002076) of China, Jiangsu Province NSF (BK20130781, BK2011722), China Postdoctoral Foundation (2012T50494), Funding of Jiangsu Innovation Program for Graduate Education (CXLX12_0136), Funding for Outstanding Doctoral Dissertation in NUAA (BCXJ12-02) and the Fundamental Research Funds for the Central Universities (NJ20120016, NP2013309). The authors acknowledge a scholarship from Dawning Information Industry.

Author information

Authors and Affiliations



W.G. conceived the project and designed the experiments with J.Yin. J.Yin, X.L. and J.Z. performed the experiments. J.Yu and Z.Z. performed the calculations. W.G., J.Yin and J.Yu analysed the data. W.G., J.Yin and Z.Z. wrote the paper. All authors discussed the results and commented on the manuscript.

Corresponding author

Correspondence to Wanlin Guo.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary information

Supplementary Information (PDF 631 kb)

Rights and permissions

Reprints and permissions

About this article

Cite this article

Yin, J., Li, X., Yu, J. et al. Generating electricity by moving a droplet of ionic liquid along graphene. Nature Nanotech 9, 378–383 (2014).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing